This proposal focuses on several important issues underlying the folding, stability, dynamics and functional state dependence of prosthetic group binding proteins. Our goal is to contribute to the understanding of the contribution of structure and dynamics to the functional competence of flavin and heme proteins, such as those involved in electron transfer. Electron transfer reactions between proteins control the generation, flow and use of energy in biological systems and one third of known enzymes are involved in oxidation and reduction. Accordingly, redox dysfunctional is directly involved with a variety of fetal or debilitating syndromes. We are most interested in exploring why many b-heme and flavin binding proteins display considerate structure and stability in their corresponding apostates and how binding modifies both the prosthetic group and the protein. Specifically, we propose to characterize the structural cooperativity of three apoproteins using hydrogen exchange, NMR relaxation, and a variety of structural NMR methods; we propose to directly quantify the redox- state dependence of dynamics of several holoproteins in an effort to understand the nature of the prosthetic group-protein interface; we propose to use our accumulated knowledge to continue the design and engineering of a series of minimalist proteins, "maquettes", with the ultimate aim of constructing functionally useful and catalytically active mini-proteins which might serve as advanced pharmaceutics and (bio)chemical reagents; and we propose to characterize the complex between cytochrome c and its binding domain in Apaf-1, an interaction that is a key event in apoptosis, programmed cell death. Each of these specific aims will require the extensive use of multi-nuclear and multi- dimensional NMR spectroscopy and will take advantage o f recent methodological developments and novel capabilities, particularly NMR relaxation methods and a high pressure NMR capability.